Seasonal Overhauls for Chillers: Chapter 1
Introduction to Seasonal Overhauls for Chillers
Remember way, way back last fall? Summer came to its bittersweet end—Back-to-school, Halloween costumes, crimson leaves, and shutting down the chiller. But did you shut it down properly and perform overhauling? If not, this module will prepare you to plan for the winter shutdown and help you understand the importance of overhauling. Skip to quiz!
Importance of Overhauls
Recall that we use chillers for cooling medium and large size buildings. As winter approaches, the weather cools outside, and temperatures can get lower. This is the time when you shut down chillers and bring boilers online.
During shut down of chiller systems, many problems like metal corrosion, scaling, and clogging of filters may arise. This can reduce systems performance. Overhauls are proactive measures to return system performance to factory condition efficiency.
Overhaul differs from maintenance. An overhaul involves:
Complete shutdown of the system.
Dismantling parts of a machine.
Repairing or replacing defective parts.
Maintenance is regular inspection of a system when the unit is operating
For example, during the overhaul of a cooling tower, we completely shut down the chiller system and inspected each component. But during maintenance, you may be on the rooftop of a building performing maintenance of a cooling tower when your chiller is still running.
Think about a car. The maintenance work of a car involves changing the transmission fluid and filter at least every 40,000 miles. In comparison, overhauling includes adding coolant to the car engine. This will stop water in our engine’s cooling system from freezing during cold winter days.
A chiller overhaul involves inspecting components and replacing critical parts as needed. We visually inspect the rotating components for scuff marks and measure their dimensions. Parts are cleaned, repaired, or replaced if faulty.
An overhaul, therefore, eliminates the causes of deterioration resulting from corrosion, abrasion, and scaling in rotating parts. This will help restore the equipment to its original condition and extend the equipment service life.
Overhauling helps in reducing energy costs. For example, any accumulation of dirt dust on the condenser coil will cause underperformance.
As dirt builds up on condenser coils, it is harder for those coils to transfer heat to the outside air. This forces the chiller to work harder and increases its energy consumption. Overhauling makes sure inefficiencies like dirty condenser coils are not present.
Shut Down and Overhauling
Now that we know the importance of overhauling, let's look at vital steps before chiller shutdown. While it might be tempting to shut out the lights and pumps for chiller shutdown, it can affect its performance. Instead, perform your shutdown with as much care as you employed during maintenance.
During the regular operation, the suspended matter is in solid form. If a proper lay-up procedure is not followed before the shutdown, these solids can settle in drums and tubes.
The first step to proper layup is to reduce the conductivity setpoint on the towers by 50%. This can be done by replacing cooling tower system water with fresh water. We need to do this two to three days before the shutdown.
Before the shutdown, non-oxidizing biocide like glycol needs to be added twice more than usual. Allow the mixture to circulate for 4-6 hours to ensure proper disinfection of all water contact areas. Next, completely drain the system and shut it down. Let’s watch a video of laying up a cooling tower.
Without proper shutdown, a few winter threats to chiller systems are:
Frozen pipes,
Blocked ducts and vents,
Dirty air filters,
A buildup of scale inside chiller tubes, and
Metal corrosion.
In order to avoid winter threats, we inspect chillers during a shutdown. The inspection checklists are used during the overhauling of chillers. In these checklists, the technician checks the different parts and assemblies of the chiller.
The inspection checklist should include:
Check the main starter and control panel,
Leak test,
Inspect condenser tubes for fouling,
Compressor motor and oil pump motor,
Change oil and filters, and
Check operation of purge unit,
Change oil in purge pump and oil separator,
Check guide vane linkage,
Check refrigerant and oil levels, and
Check the oil pump heater and purge the oil heater.
We’ll learn about these inspections in the latter topic.
Safety Measures
While performing overhauling, we need to follow some basic safety measures. These include:
Wearing safety gear,
Using the right tools,
Identifying hazards,
Chemical safety, and
Avoiding shock.
It is crucial to have the proper PPE to protect technicians from injury. While overhauling chiller systems, we should know when to wear the appropriate safety gear, which includes:
Hard hats,
Safety glasses,
Gloves,
Face masks, and
Safety-toed shoes.
Hard hats are required when working in areas where we might get injured on the head. Safety glasses are crucial because they provide protection to our eyes and prevent things from causing injury to them. The gloves are essential because they protect our hands while performing our job
Face and respiratory masks are important to protect us from hazardous fumes, sprays, infectious materials, or other sources of hazardous air quality. We wear safety-toed shoes or boots to protect our feet from falling, crushing, or rolling hazards.
It is essential to use the right tool for a specific job. Using the right tool will decrease the effort required to get a job done without causing damage to us and the equipment. That is why we have to select the proper tool to do the job well and safely.
Before jumping right into overhauling, it is critical to assess and know what we are up against. We should identify any potential hazards on each job and take proper safety precautions before doing it. It is better to take more time to get the job done right and stay safe than rush for it.
During the overhauling or shut down of chillers, we may encounter a range of chemicals that can threaten our health. Chemicals like refrigerants, lubricants, and cleaning chemicals can be problematic if they are not handled correctly.
In some cases, some chemicals can explode and cause significant injury. We should wear hand gloves when handling chemicals.
During overhauling, we should be very cautious and take preventive steps to minimize the risk of electrical shock. We have to be very careful where there is a water leak within the air handling unit. Typically, the best way to stay safe is to turn off the main circuit breaker before proceeding.
Winter shutdown poses several threats like freezing coils, clogging filters, and corrosion. Overhauls are proactive measures to protect from these threats and return system performance to factory condition efficiency. While performing overhauling, we need to follow basic safety measures.
Question #1: We shut down the chiller completely during overhauling?
True
False
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Answer: True
True. An overhaul involves complete shutdown of the system, dismantling parts of a machine, repairing or replacing defective parts.
Question #2: Why is overhauling a chiller important every winter? (select all that apply)
Overhauling reduces energy cost
Overhauling reduces the manufacturing cost of equipment
Overhauling extends the equipment service life
Overhauling encourages new technology
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Answer: Overhauling reduces energy cost
Overhauling extends the equipment service life
An overhaul improves service life and reduces energy costs.
Question #3: Arrange steps taken before seasonal shutdown in sequence?
Drain the system
Reduce the set-point on the tower
Maintain inhibitor level by adding non-oxidizing biocide
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Answer: Reduce the conductivity setpoint on the towers
Maintain inhibitor level by adding non-oxidizing biocide like glycol
Drain the system
The correct sequence is: Reduce the conductivity setpoint on the towers, Maintain inhibitor level by adding non-oxidizing biocide like glycol, Drain the system.
Question #4: Identify the threats to a chiller system during winter shut down? (select all that apply)
Frozen pipes
Dirty filters
Vaporization of water inside piping
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Answer: Frozen pipes
Dirty filters
Without proper shutdown, a few winter threats to chiller systems are: Frozen pipes, Blocked ducts and vents, Dirty air filters, A buildup of scale inside chiller tubes, and Metal corrosion.
Question #5: Which of the following checks are always included in the winterization checklist?(select all that apply)
Refrigerant recovery
Inspect condenser tubes
Compressor motor and oil pump motor
Checking spur gear backlash
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Answer: Inspect condenser tubes
Compressor motor and oil pump motor
The winterization checklist should include: Check the main starter and control panel, Inspect condenser tubes for fouling, Compressor motor and oil pump motor, and Change oil and filters.
Question #6: What measures to be considered when overhauling chillers? (select all that apply)
Wearing safety gear
Using the right tools
Wearing sweater
Listening to Podcasts during overhauls
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Answer: Wearing safety gear
Using the right tools
The safety measures that need to be considered before overhauls are: Wear safety gear, Using the right tools, Ensuring chemical safety, and Avoiding shock.